The long-term objective of this research is to understand the alterations in gene structure which cause the congenital adrenal hyperplasias. These childhood diseases together occur in about one in 5000 newborns, but persist throughout life. They are due to defects in various enzymes involved in the synthesis of adrenal steroid hormones. To study the genes coding for these enzymes, molecular probes are needed. As a prototype system, we shall make a probe for the gene for the cytochrome P450 involved in the cleavage of the cholesterol side chain, the rate limiting step in steroidogenesis. The availability of an antibody to this enzyme, termed P450scc, now makes it possible to construct and identify recombinant plasmids containing DNA complementary to the mRNA for P450scc. This P450scc cDNA, amplified by cloning in bacteria, is a molecular probe which can be used to quantify P450scc mRNA or to identify genomic DNA containing the P450scc gene in an existing human DNA "library" in Lambda phage. Nucleotide sequence analysis of this P450scc cDNA will reveal the amino acid sequence of the cytochrome P450. These data, in conjunction with sequence analysis of the P450scc genomic DNA from the Lambda phage library, will reveal the detailed structure of the gene for this enzyme. Subsequent work will entail 1) a comparison of the normal gene to the P450scc gene in patients with lesions of this enzyme, 2) quantification of the P450scc mRNA under varying hormonal influences and 3) the preparation of probes for the genes for other adrenal enzymes as antibodies to these become available.